Spatial light modulators are active devices having on them at least one row of individually controllable cells. The cells typically reflect along one of two pathways, or select between transmitting and not transmitting light. Electronic signals determine in which mode they operate. Spatial light modulators may also be manufactured with several individual rows of cells or with many rows of tightly spaced cells. The latter format, because of its cell density, is capable of producing images comparable in resolution to monochrome cathode-ray tubes.
The introduction of color to spatial light modulator systems has been problematic to date. One approach to full color systems is to use three spatial light modulators, each with a different primary color source or color filter. The three monochrome modulator images are combined into a single image to produce the desired three color picture. This system has the disadvantages of complex modulator alignment, output convergence, and excessive cost and package size of the related optic system.
The preferred approach to color light modulation, therefore, is to use a single modulator modified to produce the desired color image. Simply aligning a matrix of colored windows above the matrix of individual cells, however, is not satisfactory. The unmodulated light striking a reflective modulator is supplied externally to the individual cells and off of the final viewing optical axis. Incident light therefore passes through the filter window structure twice before being observed by the human eye. The modulated light therefore passes through two different colored window elements. The requisite geometry is prohibitively complex. In transmissive modulator systems similar problems occur. The color filters are typically sandwiched between the transparent panels during manufacture, making the already complex problem even more difficult and lowering yields.
Therefore a need has risen for a single modulator color system which is non-stressing to the individual elements, provides precise and accurate placement of the dye material relative to the cells, and whose dyes have acceptable optical and mechanical properties, and does not affect the steps of the monochrome modulator process.